1. Field of the Invention
The present invention relates to a fitting for measuring and regulating the flow rate of a medium, for example, a hydraulic medium, through a pipeline.
2. Description of the Background Art
Fittings of this type can be used for various flow mediums; in particular, they are used in heating and cooling systems to indicate the flow of a particular medium in the various branch lines. Physically, the flow indication is a measurement of the instantaneous flow rate (volume per unit of time) in dependence of the flow velocity; an indicator element shows the instant flow rate per unit (L/min.).
Often, such flow meters are combined with throttle elements for adjusting the flow to a certain rate, for example, a ball valve, a valve etc., which are either integrated in the fitting housing or are installed separately in the branch line.
A known flow meter of this type is formed of a cylindrical housing, which can be used in a flow channel in a forward flow (DE 31 15 572 A1). This housing has a pipe segment that is made of transparent material and serves as an inspection glass, in which a piston is movable against the force of a spring, the position of which is determined by the rate and velocity of the flowing medium and is visible through side openings, that is, windows in the housing. A ball valve for regulating the flow is arranged downstream from the measuring and indicator element.
With this device, the flow rate is measured in the main stream, the medium, however, continuously flows through the inspection glass. As a result, deposits settle on the inner wall of the inspection glass and successively decrease the transparency of the inspection glass, until, finally, the indicator is no longer recognizable. The deposits are floating particles, which in systems of this kind are usually distributed in the medium in a certain concentration. The floating particles are mainly dirt particles and residue from corrosion in various system components, for example, pipelines, boilers, heat exchangers, fittings, pumps etc.
Furthermore, the ball valve used in this device for the adjustment of the flow rate is not very well suited for a precise adjustment, because its angle of rotation is only 90 degrees, which severely restricts the dispersement capacity.
In a further known fitting of this class and type and one that is also used in the forward flow, a bypass line is flanged to the outside of the main housing and axis-parallel to the main flow line (DE 82 20 193 U1). The bypass line also has a window and includes, as a measuring section, a pipe segment through which a partial flow passes and which is made of transparent material. Inside the pipe segment is a corresponding movable spring-coil measuring piston, which at the same time is the indicator element. The indicator must be scaled in such a way that the entire flow, that is, primary and secondary flow, is shown.
To eliminate the need of a constant flow through the bypass channel, thus limiting the dirt deposits from the flow medium on the measuring devices, each connector of the bypass channel to the housing has a shut-off valve so that the partial flow only has to be released when the flow rate is to be determined. The manufacture and installation of such a fitting is very costly and labor intensive, in particular, numerous gaskets are needed. Besides, both shut-off valves must be open for a correct measurement; they only serve a purpose when they are completely shut off immediately after taking the measurement.
The disadvantages of a constant flow, or at least a flow during the measuring process, through the transparent pipe segments are avoided by providing a fitting that is also used in the forward flow, whereby a flow meter device having a measuring element and an indicator element, is mounted in the opening of a side connecting piece, thus closing it off to the outside (EP 0 943 901 A1). The side connecting piece thereby forms a side chamber, which in turn forms a bypass channel with its forward and reverse flow. The flow meter device itself is designed so that a rebounding plate of the measuring part that is impacted by the partial flow is arranged in the bore of a pipe segment that feeds the forward flow to the side chamber, and which is connected, via a longitudinally slidable connecting rod that is guided in an axial bore, with an indicator disk of the indicator element that is arranged on the outside of the side connecting piece.
Although this flow meter also has a ball valve for the adjustment of the desired flow rate, the single-hole mounting of the flow meter device significantly simplifies the assembly of the fitting. Its primary advantage, however, is that the indicator element, although wetted by the flow medium, is virtually completely separated from the flow so that the readability stays intact even without maintenance.
Basically, it is also common to combine a flow meter that is used in reverse flow with a distributor valve in such a way that the inspection glass of the flow meter and the closure body of the control valve form a sort of spindle, which, when turned towards the housing, allows both an adjustment of the opening width of the flow opening and the reading of the flow rate at the same time (DE 35 09 718 C2).
Whereas with this known distributor valve the frontal member of the flow meter and the position indicator rod are both movably connected to the valve closure body, thus forming a one-piece spindle, there is also known a flow meter device, which includes a rotatable inspection glass located in a spindle housing as well as a valve closure body, which is non-rotatably connected to the inspection glass but is axially movable (EP 1 130 364 A1). With this fitting, the measuring and indicator device remain stationary, whereas the turning of the inspection glass merely moves the valve closure body up and down in an axial direction for actuating the control valve.